Rectifier and like device based upon the use of mercury vapor



Aug. 4', 1931; A. BECQ 1,817,799

RECTIFIER AND LIKE DEVICE BASED UPON THE USE OF MERCURYVAPOR Filed March 5, 1926 2 Sheets-Sheet 1 I t 5 r I 5 1 I 1 I 1 I 1 5 I Au 4, 1931. A B 1,817,799

RECTIFIER AND LIKE DEVICE BASED UPON THE USE OF MERCURY VZAPOR Filed March 5, 1926 2 Sheets-Sheet 2 Patented Aug. 4, 1931 UNITED STATES ANDRE BECQ, OF PARIS, FRANCE, ASSIGNOB, BY MESNE ASSIGNMENTS, TO GENERAL PATENT orrlcla ELECTRIC COMPANY, A CORPORATION OF NEW YORK RECTIFIER AND LIKE BASED UPON THE USE OF MERCURY VAPOR Application filed larch 5, 1926, Serial No. 92,529, and in France larch 14, 1925.

, It is a known fact that in order to operate a rectifier of the mercury vapor type, the cathode must comprise an incandescent point which will emit electrons, the apparatus being lighted in a'direct manner (by induction) or in an indirect manner (by contact), or by like means.

In the case of indirect lighting, an ncandescent point is formed by momentarily starting an are between the mercury of the cathode and an auxiliary electrode.

As a general rule, for rectifiers with glass bulbs, the said auxiliary electrode consists of mercury or of graphite. The bulb is inclined so as to bring the electrode into contact with the mercurv of the principal cathode, this being performed by hand or by automatic means.

For rectifiers with metallic recipients-the g0 auxiliary electrodev consists of a movable metal rod which can be'immerged in the mercury of the cathode by means of an electromagnet..

In both cases, when contact is. made between the auxiliary electrode and the main cathode, this will close a circuit, termed arestarting circuit, carryinga suitable current which may be continuous or alternating according to circumstances. If in these con-,

ditions-inthe first case by inclining the bulb in the other direction and in the secend case byraising the metal rod-the said electrodes are separated, the spark thus produced will serve to start-,the main 'oropera- 5 tive are; it is however necessary that either the work circuit, or what is termed the exciting circuit, shall have been preliminarily closed.

According to my invention, the mercury 40 vapor apparatus is started in the general manner above disclosed, but the mechanical action for bringing the operative electrodes into contact and then separating them, is obtained by the use of a device which is constructed on the two-metal principle (thermostatic device). The starting circuit of the rectifier is supplied with a reduced amount of energy in the form of heat, and the heat actsin turn-,either directly or indirectly, in any suitable manner, upon the two-metal device and thus produces the mechanical motion ofthe latter and the displacement of the electrodes secured thereto.

In my said invention, the heat necessary for the operation of the two-metal device may be obtained directly or indirectly by the Joule efl'ectby means of a suitable electric current. or in other casesa part of the heat is emitted either by the rectifier itself when functioning. or by an adequate source of heat.

A single two-metal element (thermostatic strip) or a plurality of such elements having diflerent constituents may be employed, such elements having a suitable shape and being arranged and attached in such manner as to afford the necessary mechanical action. In the improved arrangement, such action can be either slow or abrupt, and in the lattercase the two-metalelements or strips will be properly curved and imbedded'.

The arrangements which connect the mixiliary electrodes to the movable part of twometal element. and which connect the fixed recipient of the rectifier to the stationary part of said two-metal element-, are to becarried out-i in accordance withthe characterist-ics of the auxiliary electrode and of the apparatus. i

It is further optional as concerns the invention that the aforesaid mechanical ef fects will produce: (a) a displacement of the auxiliary electrode relatively to the main fixed cathode or relatively to another electrode; (1)) a displacement of the main cathode relatively to the fixed auxiliary-electrode or another electrode: (0) the simultaneous displacement of the auxiliary'electrode and the cathode relatively to one another or relatively to other electrodes.

My said invention is applicable to all devices employing mercury vapor. The electrical arrangement of the auxiliary electrode in thearc-starting circuit can be carried out in a great variety of ways accord ing to circumstances.

Finally, it should be noted that the invention afi'ords not only the means for acting in a simple manner from the exterior to displace electrodes or elements disposed in a recipient of any kind, but it also affords means for effecting useful deformations of such elements.

In the appended drawings which are given by way of example:

Figure 1 shows an arc-starting device for use with a glass bulb, employing a single two-metal element which is directly heated.

Figure 2 shows diagrammatically another device for the arc-starting circuit of a rectifierv Figure 3 shows diagrammatically a device for the distant observing or checking of the rectifier shown in Fig. 1.

Figures 4, 5 and 6 show various positions of the two-metal element during the starting of the arc.

. Figure 7 shows details of the construction of the two metal thermostatic elements.

Referring to Figure 1, it is observed that tothe movable end I) of a two-metal element.

0 whereof the other end (2 is suitably inserted into the glass bulb and serves as a terminal for the current. The electrode a which is mechanically secured to the twometal element a is electrically insulated therefrom by the insulating member 6 and is electrically connected by the flexible conductor f with the terminal 9. The movable end of the said two-metal element is electrically connected in a permanent manner with the mercury of the cathode 2' by the elect-rode h. In the inoperative position the electrode a is slightly immersed in the mercury of the principal cathode 2'. It has been stated that it will suflice, in order to start the main operative arc, to set up a local are by separating the electrodes a and 2'. The resulting electric circuit is shown in the dotted lines in Figure 1 in which r is a suitable resistance; if a suitable E. M. F. is applied between the points is and Z, the energy dissipated by the Joule effect in the two-metal element used as a conductor in the electric circuit Z 1' (Z c b h a is will effect the deformation of the said element, so that the point I) will assume the position B; the disposition of the two-metal element is shown in the dot-and-dash lines. The electrode a which is secured to the end B of the two-metal element and which formed the starting circuit Z at 9v 7 a 2' It will now leave the mercury and will start an arc at the surface of the mercury. .This

movement continues until the arc is broken and the arc-starting circuit is interrupted. The main arc is thus set up, i. e. the rectifying device enters into action, and a simple device willcut oil the E. M. F. which was applied at k and Z. The electrodes now assume the inoperative position and are ready auxiliary electrode to the end of the said two-metal element, and the latter will serve solely as a conductor in a single arc-starting circuit. The rectifier is set in operation bythe above-mentioned process, with out the use of auxiliary relays.

Figure 2 shows by way of example a constructional form of the said arrangement, employed for a glass bulb rectifier which serves to rectify the two waves of a single-phase alternating current. The auxiliary electrode a is secured to the movable end of a two-metal element 0 whereof the stationary end (Z is attached to a metal rod 0 which is fused into the glass bulb and forms a current terminal. In the inoperative position of the device, the positions of the several parts are such that the electrode a is immersed in the mercury of the cathode 2". In the present example, an alternating current E. M. F. is applied between the rod 0 and the cathode 2' by means of an auxiliary winding is, Z of the main transformer. In addition to the main arc-starting circuit thus afforded, themain circuit of the apparatus comprises, in the known manner, the secondary p, g of the main transformer which sends through the bulb (by means of the anodes z) a rectified current into the work circuit u 7), the primary :1: y of the said transformer is supplied by the source of alternating current 8.

In these conditions, the apparatus being inoperative, if a current is sent into the primary a: g of the main transformer, the E. M. F. supplied by the winding k Z to the arcstarting circuit causes the heating of the metal parts by the effect of the current, and

hence the deformation of the two-metal elecontact with the mercury and the preceding upon the first breaking of the arc-starting circuit. The main arc, being started, will cause the heating of the two-metal element so as to cause the deformation of the latter, and the arc-starting circuit thus remains open as long as the main arc subsists. Should the main are be stopped for any cause, the twometal element will become cooled and will bring the said electrode to the initial position for the next arc-starting operation.

Itis advantageous that the apparatus should be lighted as rapidly as possible, either in the case of the first lighting or a lighting after an accidental extinguishing, and we operate as follows: firstly. the twometal element must heat up rapidly so as to quickly separate the mercury from the arcstarting electrode: the said element must be thin and it thus has but little mechanical strength: secondly. as soon as the main arc is extinguished. the two-metal element will bring the lighting electrode into contact .with the mercury.

But these two conditions are hhrdly compatible. since a thin two-metal strip will cause a considerable movement of the electrode which it carries. and the electrode must be given a certain time in order to attain the mercury surface when the main are has been put out. this being contrary to what is sought for.

To overcome this difliculty, the two-metal element is made of two parts which ha! different properties and are placed in contrary directions (Figure 4). One part It is thin and tends when heated to raim the electrode a: the other part e is thick and tends when heated to lowe-r the whole device towards the mercury. When the currentis sent into the said two-metal device. the part b will heat up rapidly and will separate the electrode from the mercury (Fig. 5): the part e will then become slowly heated and will bring the electrode a near the mercury (Fig. 6) in such manner that it may be rapidly immerged therein should the bulb be accidentally extinguished. As indicated by Fig. 7 the relatively thick thermostatic element 0 may include a pair of strips 0' and I) made of different metals while the relatively thin part b may include-the same elements which have their positions reversed with respect to those of theelement e.

In the aforesaid method the permanentheating which is produced by the main arc may be employed. but it is obvious that the permanent heating and deformation of the two-metal element which are neces ary to hold the arc-starting circuit open. may be effected by the upkeep arc in the case in which the apparatus has an upkeep circuit.

or simultaneously by the main arc and the upkeep arc.

I may also employ the auxiliary electrode in the first place as an arc-starting electrode and then as an upkeep electrode.

In all cases. the protection. of the arcstarting circuit against any excess of tension by placing a protecting device known per se in this circuit such as a fusible element. current-limiting device, or the like is as umed. I

By the disposition of the two-metal element in the arc-starting circuit as hereinbefore described. we obtain the following results:

1. The electric energy required to effect the deformation of the two-metal element by heating the samerepresented by an alternating E. M. F. in the present example is furnished by a source of current which supplies the apparatus by means of an auxiliary transformer, or by both. For suitable dimensions of the two metal elementand the auxiliary element, it is feasible by varying the E. M. F. to regulate at willthe rate at which the auxiliary electrode is separated from the mercury of the cathode i. e. the duration of the auxiliary arc, and also to regu late the time elapsed between the moment when the current is sent into the windings of the transformers and the .moment of starting of the firstauxiliary arc and the principal arc.

The impedance. of the arc-starting circuitmay also be variable, and its reactance serves chiefly to modify the energy and the duration of the auxiliary arc.

.The choice of the aforesaid elements should also be made with reference to the calorific inertia as regards the cooling of the device consisting of the auxiliary electrode, and the two-metal element. which inertia determines the time elapxd between the extinguishing of the main arc and the instant in which the auxiliary electrode returns into contact with the cathode in order to start the main arc. Finally. the apparatus is operated in such manner thatthe displacements of the cathode spot and of the main arc will notproduce mechanical effects of aprejudicial nature upon the device consisting of the electrode and the two-metal element. I

2. Since the state of the arc-starting circuit characterizes ateach instant the operating phase of the rectifier. this circuit can be used as a checking means. Fig. 3 shows by wayof example an arrangement for the distant observation of the working of the single-phase rectifier (Figure 2) by means of a pilot lamp. The coil 5 of a double-acting relay is placed in the arc-starting circuit 0 k I i: the circuit of the pilot lamp w is supplied by the main current line a and comprises a resistance 17; when current is 'is formed; it will be extinguished when circuit means to supply heating the arc is broken or the current fails. In this way a simple optical observation of the working of the apparatus, by the use of the arc-starting circuit is provided.

Obviously, the aforesaid combination is applicable to all apparatus based upon the mercury vapor arc, operating in the abovementioned conditions. In particular, the said combination will as above stated afford a means for effecting from the exterior and in a simple manner the displacement and optionally the deformation of the auxiliary electrode, and further the displacement (and the obligatory) deformation of the mercury of the cathode, which displacements may be simultaneous or not, irrespectively of the container in use for the mercury vapor apparatus, such as glass, quartz, metallic recipient, or the like.

Claims:

1. In a mercury vapor rectifier, the combination of a two-metal thermostatic support fixed only at one of its ends, an auxiliary are starting electrode fixed to the other end of said support and auxiliary arc-starting currents to said support.

2. In a mercury vapor rectifier, the combination of a two-metal thermostatic support fixed only at one of itsends and provided with successive parts of difierent thicknesses and contrary curvatures, and an auxiliary are starting electrode fixedto the free end of said support.

3. In a mercury vapor rectifier, the combination of a two-metal thermostatic support fixed only at one of its ends and provided with successive parts of difierent thicknesses and contrary curvatures, and an auxiliary are starting electrode fixed to the free end of said support and arranged to be moved as a whole with said support.

4. In a rectifier, the combination of a mercury cathode, a two-metal thermostatic support fixed only at one of its ends, an auxiliary are starting electrode fixed to the free end of said support and arranged to be moved into and out of engagement with said cathode in response to change in the temperature of said support and auxiliary arc-starting circuit means to. supply heating current to said support.

5. In a mercury vapor rectifier, the com bination of a two-metal thermostatic support fixed only at one of its ends, an auxiliary are starting electrode fixed to and arranged to move as a whole with the free end of said support and auxiliary arc-starting port fixed only at one of its ends, an auxili ary are starting electrode. fixed to the other end of said support and arranged to be moved transversely of the longitudinal axis of said support and-auxiliaryarc-starting circuit means to supply heating current to said support.

In testimony whereof I aflix my signature.

ANDRE Y BECQ. 

